a normal conductive rf photo-injector for high repetition rate x-ray free electron lasers

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A normal conductive RF photo-injector for A normal conductive RF photo-injector for high repetition rate X-ray free electron lasershigh repetition rate X-ray free electron lasers

(and ERLs)(and ERLs)

Fernando SannibaleFernando Sannibale

Lawrence Berkeley National LaboratoryLawrence Berkeley National Laboratory

48th ICFA Advanced Beam Dynamics Workshop on Future Light Sources - SLAC, March 2, 2010

Array of 10 configurable FEL beamlines, up to 20 X-ray beamlines100 kHz CW pulse rate, capability of one FEL having MHz rate

Independent control of wavelength, pulse duration, polarizationEach FEL configured for experimental requirements;

seeded, attosecond, ESASE, mode-locked, echo effect, etc Beam transport and

switchingCW superconducting linac2.5 GeV

Laser systems,timing & synchronization

Low-emittance, MHz bunch rate

photo-gun≤ 1 nC

≤1 mm-mrad

Injector

Laser heater Bunch

compressor


The LBNL FEL SchemeThe LBNL FEL SchemeA NC CW RF Photo-Injector

for FEL ApplicationsF. Sannibale

Experimental Halland Laboratory Space

FEL and X-Ray Beamline Array Accelerator in Tunnel

Portal

Injector

ALS

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Great Valley Group (Kgv)

Orinda Formation (TO)

ALS

Bevatron site

DESY - Zeuthen Seminar, Berlin, February 8, 2010

NGLS Site at LBNLNGLS Site at LBNLA NC CW RF Photo-Injector


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High-High-brightness, brightness,

1 MHz rep-rate 1 MHz rep-rate electron gunelectron gun

FEL Physics,FEL Physics,\Undulators\Undulators

Laser systems,Laser systems,timing & synchronizationtiming & synchronization

Beam Beam manipulation manipulation

and and conditioningconditioning

Beam distribution and Beam distribution and individual beamline tuningindividual beamline tuning

~2 .5 GeV CW ~2 .5 GeV CW superconducting linacsuperconducting linac

DESY - Zeuthen Seminar, Berlin, February 8, 2010

An R&D Program andAn R&D Program and Studies for the Critical PartsStudies for the Critical Parts

A NC CW RF Photo-Injectorfor FEL Applications

F. Sannibale

Cathode/laserCathode/laser

Most of such R&D areas are fundedMost of such R&D areas are funded

High-High-brightness, brightness,

1 MHz rep-rate 1 MHz rep-rate electron gunelectron gun

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• repetition rates up to ~ 1 MHzrepetition rates up to ~ 1 MHz

• charge per bunch from few tens of pC to ~ 1 nC,charge per bunch from few tens of pC to ~ 1 nC,

• sub 10sub 10-7-7 (low charge) to 10 (low charge) to 10-6-6 m normalized beam emittance, m normalized beam emittance,

• beam energy at the gun exit greater than ~ 500 keV (space charge),beam energy at the gun exit greater than ~ 500 keV (space charge),

• electric field at the cathode greater than ~ 10 MV/m (space charge limit),electric field at the cathode greater than ~ 10 MV/m (space charge limit),

• bunch length control from tens of fs to tens of ps for handling space bunch length control from tens of fs to tens of ps for handling space charge effects, and for allowing the different modes of operation,charge effects, and for allowing the different modes of operation,

• compatibility with significant magnetic fields in the cathode and gun compatibility with significant magnetic fields in the cathode and gun regions (mainly for emittance compensation)regions (mainly for emittance compensation)

• 1010-9-9 - 10 - 10-11-11 Torr operation vacuum pressure (high QE photo-cathodes), Torr operation vacuum pressure (high QE photo-cathodes),

• “ “easy” installation and conditioning of different kind of cathodes,easy” installation and conditioning of different kind of cathodes,

• high reliability compatible with the operation of a user facility.high reliability compatible with the operation of a user facility.

To achieve the LBNL FEL goals, the electron source should To achieve the LBNL FEL goals, the electron source should simultaneouslysimultaneously allow for: allow for:


F. Sannibale


Electron SourceElectron SourceRequirementsRequirements


F. Sannibale

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• Based on Based on mature and reliable normal-conducting RF and mechanical technologiesmature and reliable normal-conducting RF and mechanical technologies..

The LBNL The LBNL normal-conductingnormal-conducting design tries to satisfy design tries to satisfy all the LBNL FEL requirements simultaneously. all the LBNL FEL requirements simultaneously.

Frequency 187 MHz

Operation mode CW

Gap voltage 750 kV

Field at the cathode 19.47 MV/m

Q0 30887

Shunt impedance 6.5 M

RF Power 87.5 kW

Stored energy 2.3 J

Peak surface field 24.1 MV/m

Peak wall power density 25.0 W/cm2

Accelerating gap 4 cm

Diameter 69.4 cm

Total length 35.0 cm

• 187 MHz compatible with both 1.3 and 1.5 GHz super-conducting linac technologies.187 MHz compatible with both 1.3 and 1.5 GHz super-conducting linac technologies.

K. Baptiste, et al, NIM A 599, 9 (2009)

J. Staples, F. Sannibale, S. Virostek, CBP Tech Note 366, Oct. 2006

2009 Free Electron Laser Conference - Liverpool - August 26, 2009

• At the At the VHF frequencyVHF frequency, the cavity structure is large enough to withstand the heat load , the cavity structure is large enough to withstand the heat load and and operate in CW mode operate in CW mode at the required gradients. at the required gradients.

• Also, the Also, the long long RFRF allows for large apertures and thus for allows for large apertures and thus for high vacuum conductivityhigh vacuum conductivity..


The LBNL VHF RF GunThe LBNL VHF RF GunA NC CW RF Photo-Injector


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• The The long RF wavelength long RF wavelength allows for allows for large apertures large apertures and for and for high vacuum conductivityhigh vacuum conductivity. The vacuum system has been . The vacuum system has been

designed to achieve an operational vacuum pressure down designed to achieve an operational vacuum pressure down into the low into the low 1010-11-11 Torr range. Torr range. NEGs pumps are used (very NEGs pumps are used (very

effective with Heffective with H22O and OO and O22). This arrangement will allow testing ). This arrangement will allow testing

a variety of cathodes including "delicate" multi-alkali and/or a variety of cathodes including "delicate" multi-alkali and/or GaAs cathodes.GaAs cathodes.

The nominal laser illumination The nominal laser illumination configuration for the cathode is configuration for the cathode is quasi-perpendicular with laser quasi-perpendicular with laser entrance in the beam exit pipe.entrance in the beam exit pipe.

An additional 30 deg laser entrance port has been added to allow An additional 30 deg laser entrance port has been added to allow testing of more exotic cathodes (surface plasma wave cathodes, ...)testing of more exotic cathodes (surface plasma wave cathodes, ...)

• Cathode area designed to operate with a Cathode area designed to operate with a vacuum load-lock vacuum load-lock mechanismmechanism for an easy in-vacuum replacement or “in situ” for an easy in-vacuum replacement or “in situ”

reconditioning of photocathodes.reconditioning of photocathodes.


A Cathode Test FacilityA Cathode Test FacilityA NC CW RF Photo-Injector


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PEA Semiconductor: Alkali Antimonides eg. SbNaPEA Semiconductor: Alkali Antimonides eg. SbNa22KCs, CsKKCs, CsK22Sb, … Sb, … - <~ps pulse capability (studied at BOING, INFN-LASA, BNL, Daresbury, LBNL, ….)- <~ps pulse capability (studied at BOING, INFN-LASA, BNL, Daresbury, LBNL, ….)- reactive; requires <~ 10- reactive; requires <~ 10-10-10 Torr pressure Torr pressure- high QE > 1%- high QE > 1%- requires green/blue light (eg. 2- requires green/blue light (eg. 2ndnd harm. Nd:YVO4 = 532nm) harm. Nd:YVO4 = 532nm)- for nC, 1 MHz reprate, ~ 1 W of IR required - for nC, 1 MHz reprate, ~ 1 W of IR required

PEA Semiconductor: Cesium Telluride CsPEA Semiconductor: Cesium Telluride Cs22Te Te (used at FLASH for example)(used at FLASH for example)

- <~ps pulse capability- <~ps pulse capability- relatively robust and un-reactive (operates at ~ 10- relatively robust and un-reactive (operates at ~ 10-9-9 Torr) Torr) - successfully tested in NC RF and SRF guns- successfully tested in NC RF and SRF guns- high QE > 1%- high QE > 1%- photo-emits in the UV ~250 nm (3- photo-emits in the UV ~250 nm (3rdrd or 4 or 4thth harm. conversion from IR) harm. conversion from IR)- for 1 MHz reprate, 1 nC, ~ 10 W 1060nm required- for 1 MHz reprate, 1 nC, ~ 10 W 1060nm required

FLASHFLASH

INFN-LASAINFN-LASA


Photo-Cathodes/LasersPhoto-Cathodes/LasersSystems for the LBNL GunSystems for the LBNL Gun


F. Sannibale

• Cathodes from INFN-LASA in MilanoCathodes from INFN-LASA in Milano• Laser from Q-PeakLaser from Q-Peak

• R&D for the development at LBNLR&D for the development at LBNL• Laser from LLNLLaser from LLNL

Possibility of testing other cathodesPossibility of testing other cathodes

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• EXAMPLE: No pre-buncher or buncher. Just main linac cavitiesEXAMPLE: No pre-buncher or buncher. Just main linac cavities• Velocity bunching by de-phasing the first cavityVelocity bunching by de-phasing the first cavity

• Emittance compensation by a single solenoid (plus embedded bucking coil)Emittance compensation by a single solenoid (plus embedded bucking coil)

• Multi-Objective Genetic Multi-Objective Genetic Algorithms optimizationAlgorithms optimization, trading , trading

between final emittance and between final emittance and bunch length.bunch length.

ASTRA – 10k particles

2009 Free Electron Laser Conference - Liverpool - August 26, 2009

• Work in progress but already showed the VHF gun capability to operate in a FEL Work in progress but already showed the VHF gun capability to operate in a FEL scheme scheme


Ongoing BeamOngoing BeamDynamics StudiesDynamics Studies


F. Sannibale

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The Boeing gun has achieved 25% duty cycle operation at 433 MHz.The Boeing gun has achieved 25% duty cycle operation at 433 MHz.

A VHF (144 MHz) gun is used at the ELSA 19 MeV linac and A VHF (144 MHz) gun is used at the ELSA 19 MeV linac and produces high charge-low emittance beams within a 150 produces high charge-low emittance beams within a 150 s s

macropulse at 10 Hz repetition rate.macropulse at 10 Hz repetition rate.

D. Dowell, et al., Appl. Phys. Lett., 63 (15), 2035 (1993).

R. Dei-cas, et al., NIM A, 296, pp. 209 (1990).R. Dei-cas, et al., NIM A, 331, pp. 199 (1993).J.-G. Marmouget, et al., EPAC 2002, Paris, France, June 2002, p. 1795.D. Guilhem, et al., EPAC 2006, Edinburgh, Scotland, July 2006, p. 1927.

A Los Alamos/AES completed the RF test of a 700 MHz normal-A Los Alamos/AES completed the RF test of a 700 MHz normal-conducting RF gun where a sophisticated and state of the art cooling conducting RF gun where a sophisticated and state of the art cooling

system allows the gun to operate in CW mode.system allows the gun to operate in CW mode.S.S. Kurennoy, et al., NIM A 528, 392 (2004).

A 700 MHz CW normal conducting gun was studied at JLAB.A 700 MHz CW normal conducting gun was studied at JLAB. R. A. Rimmer, PAC05, pag. 3049.

Brookhaven National Laboratory – April 17, 2009

A 144 MHz CW normal conducting gun was studied at BNL.A 144 MHz CW normal conducting gun was studied at BNL. X. Chang, et al., PAC07, pag. 2547.


CW or Quasi-CW RF GunsCW or Quasi-CW RF GunsA NC CW RF Photo-Injector


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• The cavity design The cavity design finalizedfinalized


Cavity Design CompletedCavity Design CompletedA NC CW RF Photo-Injector


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• Most of the cavity is being fabricated at the LBNL mechanical shopMost of the cavity is being fabricated at the LBNL mechanical shop

• Fabrication completion in early spring 2010.Fabrication completion in early spring 2010.• First cold RF test succesfully performed.First cold RF test succesfully performed.


And in construction!And in construction!A NC CW RF Photo-Injector


13• Expected delivery at LBNL in March 2010Expected delivery at LBNL in March 2010

• The 120 kW CW RF amplifier required to operate the VHF gun is being The 120 kW CW RF amplifier required to operate the VHF gun is being developed and manufactured by ETM Electromatic.developed and manufactured by ETM Electromatic.


The RF Power SourceThe RF Power SourceA NC CW RF Photo-Injector


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All the photo-injector system will be accommodated in the All the photo-injector system will be accommodated in the existingexisting ALS Beam Test Facility (BTF) for full characterization.ALS Beam Test Facility (BTF) for full characterization.

The BTF footprint is large enough to accommodate also the structures The BTF footprint is large enough to accommodate also the structures to accelerate the beam to few tens of MeV.to accelerate the beam to few tens of MeV.


F. Sannibale


The VHF Gun Test FacilityThe VHF Gun Test FacilityA NC CW RF Photo-Injector


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Fully funded (to be completed by 2010)Fully funded (to be completed by 2010)

• Perform cold and full power RF tests of the VHF cavityPerform cold and full power RF tests of the VHF cavity

• Demonstrate the system vacuum performanceDemonstrate the system vacuum performance

• Install and characterize the first generation cathode.Install and characterize the first generation cathode.

• Characterize the electron beam at the gun energy (750 kV) at full Characterize the electron beam at the gun energy (750 kV) at full repetition raterepetition rate


F. Sannibale

In phase I, only the gun, the vacuum In phase I, only the gun, the vacuum load lock system and a low energy load lock system and a low energy

beam diagnostics installed in the BTFbeam diagnostics installed in the BTF


Phase I Test PlanPhase I Test PlanA NC CW RF Photo-Injector


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Requires funding continuationRequires funding continuation

• Develop and install accelerating section Develop and install accelerating section for few tens of MeV energyfor few tens of MeV energy

• Develop and install high energy Develop and install high energy diagnostic beamlinediagnostic beamline

• Perform full characterization of the Perform full characterization of the beam parameters at high energy beam parameters at high energy (probably at low repetition rate)(probably at low repetition rate)


F. Sannibale


Phase II Test PlanPhase II Test PlanA NC CW RF Photo-Injector


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Does the cavity go through the door?Does the cavity go through the door?

Yes, it does!!!Yes, it does!!!


Fundamental QuestionFundamental QuestionA NC CW RF Photo-Injector


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K. Baptiste, B. Bailey, D. Colomb, J. Corlett, S. De Santis, J. K. Baptiste, B. Bailey, D. Colomb, J. Corlett, S. De Santis, J. Feng, R. Kraft, S. Kwiatkowski, D. Li, M. Messerly, R. Muller, H. Feng, R. Kraft, S. Kwiatkowski, D. Li, M. Messerly, R. Muller, H. Padmore, C. Papadopoulos, G. Portmann, M. Prantill, J. Qiang, Padmore, C. Papadopoulos, G. Portmann, M. Prantill, J. Qiang,

F. Sannibale, J. Staples, T. Vecchione, W. Wan, R. Wells, L. F. Sannibale, J. Staples, T. Vecchione, W. Wan, R. Wells, L. Yang, A. Zholents, M. Zolotorev.Yang, A. Zholents, M. Zolotorev.

Contributions: J. Byrd, D. Dowell, E. Jongeward, A. Nassiri, Contributions: J. Byrd, D. Dowell, E. Jongeward, A. Nassiri, R. Rimmer, T. M. Huang, S. Lidia, J. McKenzie, Vadim R. Rimmer, T. M. Huang, S. Lidia, J. McKenzie, Vadim

Veshcherevich, S. Virostek, W. Waldron, ... .Veshcherevich, S. Virostek, W. Waldron, ... .


The VHF Injector TeamThe VHF Injector TeamA NC CW RF Photo-Injector


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J. Staples, F. Sannibale, S. Virostek, "VHF-band Photoinjector", CBP Tech Note 366, October 2006

S. Lidia, et. al., ”Development of a High Brightness VHF Electron Source at LBNL”, Proceedings of the 41st Advanced ICFA Beam Dynamics Workshop on Energy Recovery Linacs, Daresbury Laboratory, UK, May 21-25, 2007.

J. W. Staples, et al., "Design of a VHF-band RF Photoinjector with MegaHertz Beam Repetition Rate". 2007 Particle Accelerator Conference, Albuquerque, New Mexico, June 2007.

K. Baptiste, et al., "The LBNLnormal-Conducting RF gun for free electron laser and energy recovery linac applications", NIM A 599, 9 (2009).

K. Baptiste, et al., Status of the LBNL normal-conducting CW VHF photo-injector, Proceedings of the 2009 Particle Accelerator Conference, Vancouver, Canada, May 2009.

K. Baptiste, et al., Status and plans for the LBNL normal-conducting CW VHF photo-injector, Proceedings of the 2009 Free Electron Laser Conference, Liverpool, UK, August 2009.


The VHF Gun ReferencesThe VHF Gun ReferencesA NC CW RF Photo-Injector
